SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications From Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 27, 2017	Aug. 28, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses	$ 239.0	$ 231.7
Income from continuing operations before income taxes and equity method investment earnings	243.6	254.7
Income tax expense	(120.0)	(169.2)
Net income attributable to Conagra Brands, Inc.	152.5	186.2
Reclassification out of accumulated other comprehensive loss | Net prior service benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses	(0.1)	(0.9)
Income from continuing operations before income taxes and equity method investment earnings	(0.1)	(0.9)
Income tax expense	0.0	0.3
Net income attributable to Conagra Brands, Inc.	$ (0.1)	$ (0.6)